implement inlineStr. closes #112 #161

[JanMarvin]

what does it do

This PR implements basic handling of inlineStr. It reads the inlineStr <is> node and handles it as if its a <v> node with t="str". So this:

<c r=... >
    <is>
        <t>text</t>
    </is>
</c>

is for our import logic identical to this

<c r=... t="str">
    <v>text</v>
</c>

how was it implemented

I've implemented it as type 5 so once it's imported as inlineStr it can be written as inlineStr. My initial PR was quite small, only a few lines, but when testing it, reading with read.xlsx() directly from files was slow as hell. Most likely due to hundreds of runs through the same large string. Therefore I had to remove the import logic from the getCellInfo() file and replace it with the logic from loadworksheets(). In theory there shouldn't be a measurable speed difference and this should be beneficial since it reduces the two different approaches for the same thing to only a single (duplicated) approach. Still I didn't run any benchmarks with previous versions against this PR.

what's left for others to do

I haven't implemented any modifications for userspace functions to create, remove or modify inlineStr and I have no interest to do so. Therefore currently the only way to write inlineStrs with openxlsx is to import one, but I assume it can be implemented quite easily and might be beneficial for other reasons.

final words?

Included in this PR are minor updates caused by a new Rcpp release (completely harmless) and a modification to the LICENSE file which was outdated.

[codecov-commenter]

Codecov Report

Merging #225 (df670fc) into master (57333c1) will increase coverage by 0.15%.
The diff coverage is 92.39%.

@@            Coverage Diff             @@
##           master     #225      +/-   ##
==========================================
+ Coverage   65.44%   65.59%   +0.15%     
==========================================
  Files          34       34              
  Lines        8879     8918      +39     
==========================================
+ Hits         5811     5850      +39     
  Misses       3068     3068              

Impacted Files	Coverage Δ
R/utils.R	94.11% <ø> (ø)
src/write_file_2.cpp	0.00% <0.00%> (ø)
src/read_workbook.cpp	90.26% <95.94%> (-0.19%)	⬇️
R/workbook_read_workbook.R	89.32% <100.00%> (+0.56%)	⬆️
src/load_workbook.cpp	94.76% <100.00%> (+0.05%)	⬆️
src/write_data.cpp	62.96% <100.00%> (+1.13%)	⬆️
src/write_file.cpp	89.04% <100.00%> (+0.15%)	⬆️
R/WorkbookClass.R	57.24% <0.00%> (+0.16%)	⬆️

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[JanMarvin]

This fixes #112 #161 and #204 (probably others)

[JanMarvin]

Oh I'm not sure about the changes in src/write_file_2.cpp. They are similar to the other changes (I actually started with this file), but in my tests it was not used, therefore not sure about it. It's one of the many mysteries of openxlsx which function is called when and for what reason.